Rendered image has white "tiles"
I think you might have a duplicate ground plane in your scene that is hidden in your viewport (which is why it does not show up in the viewport rendering). If that is the case, it will still be rendered because the F12-rendering does not ignore hidden objects.

If the plane has a white material and is in exactly the same z position, it will be in conflict with the textured one. As a result, faces will show pretty much randomly from either of the two objects, creating the pattern that you can see in your rendering.

You can unhide all hidden objects with Alt+H in the 3D View.